1. Field of the Invention
The present invention relates to a stamper cleaning apparatus and, in particular, to a stamper cleaning apparatus for electrocleaning, washing with water and drying a stamper used to mold optical discs.
2. Description of the Related Art
A master board such as a stamper for use in the manufacture of discs for recording information, e.g., LP disks or optical discs, is generally manufactured in the following process.
First, an original glass board is polished. A light-sensitizing resin film is applied to the polished surface and optical etching is performed to form a desired fine pattern. Next, a thin metal film is disposed on the fine pattern surface and a covering is made of a desired thickness by electroplating with nickel. Then the covering is separated from the original glass board and a stamper is made.
However, a light-sensitizing resin film remains on the surface of this stamper. To remove this film, the following methods have been adopted: (1) an electrodegreasing cleaning method which performs electrodegreasing in a solution mixed with an alkali/surface active agent, (2) an ultrasonic cleaning method which cleans in an organic solvent using ultrasonic waves, and (3) a cleaning method that is a combination of these methods (Japanese Patent Laid-Open No. 62-214535).
Unlike conventional LP records, information recording discs and optical discs which retrieve recorded information by means of light have come to be used markedly in other fields in recent years. The width of a groove for recording
information of an optical disc is 0.5 .mu.m, 1/100 that of an LP record with its groove width of 50 .mu.m.
The size of the fine particles remaining on a stamper for molding a disc, that has been cleaned by the various cleaning methods mentioned above is 1 to 10 .mu.m. The size of various kinds of dust or fine particles deposited by a stamper thereafter (during the molding of discs) is almost the same.
Accordingly, since a groove for recording information on a conventional stamper for molding LP records (for analog use) has a size of about 50 .mu.m, as mentioned above, only cleaning at manufacturing time is needed.
On the other hand, since a groove for recording information on a stamper for molding optical discs (for digital use) is about 0.5 .mu.m, even fine particles of 1 .mu.m exert a disabling influence on information recording. In a stamper for molding optical discs, particularly, the grooves for recording information are narrow and near to each other. Therefore it is difficult to manufacture a stamper and it is expensive. A great number of optical discs must be molded using one stamper and storage for a long period of time is required.
A stamper for molding optical discs requires that cleaning be done because of dust or fine particles deposited during molding work or because of corrosion resulting from storage for a long period of time. Of course, to perform extraordinary cleaning of a stamper for molding optical discs with ease, the above electrodegreasing cleaning method and/or the ultrasonic cleaning method adopted in an ordinary stamper manufacturing process can be considered. However, it is difficult to increase the degree of effectiveness of cleaning one hundred-fold.
Also, making clean the entire work environment in which optical discs are molded can be considered. However, this requires that facilities for removing dust of 0.1 .mu.m in a work room or for removing fine particles of the same size as those dispersed in the water used are needed. These facilities cannot but be large-scale, so this method is not practical.